Pressure loaded pump or motor



Dec. 24, 1957 B. H. MOSBACHER PRESSURE LOADED PUMP OR MOTOR 2 Sheets-Shec 1 Filed Dec. 8, 1953 Dec. 24, 1957 B. H. MOSBACHER PRESSURE LOADED PUMP 0R MOTOR 2 Sheets-Sheet 2 Filed Dec. 8, 1953 United States Fatent O 2,817,297 PRESSURE LOADED PUlVIP OR MOTOR Bruce H. Mosbacher, Rockford, 11]., assignor to Geo. D. Roper Corporation, Rockford, 111., a corporation of Application December 8, 1953, Serial No. 396,931 Claims. (Cl. 103-126) This invention relates to improvements in pressure loaded gear pumps or fluid motors.

Pressure loaded pumps, particularly those of the gear type, have come into extensive use because of their exceptionally high volumetric efliciencies, which render them capable of delivering high output pressures previously unattainable with rotary pumps. In conventional pressure loaded pumps there is provided at least one pair of axially movable pressure bushings or wear plates extending substantially completely across one end face of the gears and providing a pumping seal thereat. Fluid pressure, commonly a part of the pump output pressure, is applied against the back of these pressure bushings to urge their front faces against the adjacent end faces of the gears to maintain the fluid seal thereat.

In pressure loaded pumps the pressure loading force acting against the back of each pressure bushing and urging it toward the corresponding gear is uniformly distributed across the pressure bushing. However, at the front face of the pressure bushings the opposing fluid pressure in the pumping chamber in which the gears operate is non-uniform across each pressure bushing. Here, there is -a pressure gradient extending from the pump inlet passage to the pumping chamber, which is at the minimum pressure, around to the discharge outlet from the pumping chamber, which is at the maximum pressure of the gradient. For this reason the net force on each pressure bushing at the pump inlet passage tending to move the pressure bushing toward the end face of the respective gear is substantially greater than the corresponding net force on each pressure bushing at the discharge outlet. This force unbalance across the front face of each pressure bushing tends to cause it to tilt away from the end face of the corresponding gear at the discharge outlet, breaking the pumping seal thereat, which is precisely where the seal is needed most, and .nullifying to a large extent the benefits of pressure loading. In addition, since the pressure bushings are forced more tightly against the end faces of the gears at the inlet passage, the pressure bushings are subjected to excessive wear at these locations. The power required to operate the pump is increased because of this uneven wear across the front faces of the pressure bushings, as well as because of the relatively large areas of the pressure bushings confronting the gears.

It is the purpose of the present invention to avoid the foregoing disadvantages formerly associated with pressure loaded pumps and to provide a novel pressure loading arrangement in such devices which is more effective for its intended purpose.

Accordingly, it is an object of the present invention to provide a novel and improved pressure loading arrangement for gear pumps or fluid motors.

Also, it is an object of this invention to provide a novel pressure loaded gear pump or fluid motor having a novel and simplified arrangement for maintaining an efl'ective pumping seal across end faces of the gears-which is less subject to tilting away from these end faces of the gears.

Another object of this invention is to provide a novel pressure loaded gear pump or fluid motor in which the frictional drag between the pressure loaded mechanism and the gears is minimized, while still maintaining an effective pumping seal between the high and low fluid pressure areas in the pump or motor.

A further object of the present invention is to provide a novel pressure loaded gear pump or fluid motor in which the fluid forces tending to displace the pressure loaded mechanism away from the gears to reduce the elfectiveness of the pumping seal thereat cancel each other out.

Another object of this invention is to provide novel mechanism for improving the pressure loaded sealing arrangement in a gear pump or fluid motor which is readily adaptable to standard devices of this type with only a minimum of modification thereof and which does not add stringent dimensional tolerance requirements to such devices.

A more comprehensive understanding of the present invention, as well as additional objects and advantages thereof, will be apparent from the following description of two preferred embodiments thereof illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a longitudinal section through a gear pump or fluid motor according to a first embodiment of the present invention;

Fig. 2 is an exploded perspective view showing the fluid displacement mechanism and the pressure loading arrangement therefor in the Fig. 1 device;

Fig. 3 is an end view of the Fig. 1 pump or-fluid motor;

Fig. 4 is a transverse section through the pump 0 fluid motor, taken along the line 44 in Fig. 1;

Fig. 5 is an end view of the pressure loaded member in the Fig. l embodiment;

Fig. 6 is a top view of this pressure loaded member;

Fig. 7 is a fragmentary transverse section through a pump or fluid motor which incorporates a second pres-, sure loading arrangement, in accordance with the present invention; and

Fig. 8 is a longitudinal section through the Fig. 7 pump or fluid motor, showing the pressure loaded mechanism extending contiguous to the adjacent end faces of the gears.

Referring first to the embodiment of the present invention shown in Figs. 1-6, and assuming for purposes of description that the device is to be operated as a pump, the pump casing is in the form of an oblong annular member 10 formed with intersecting cylindrical bores 11 and 12, and end plates 13 and 14 bolted to the opposite ends of member 10 and defining therewith the fluid displacement chamber of the pump at bores 11 and 12. A cylindrical bore through member 10 at the intersection of bores 11 and 12 defines arcuate housing recesses 10a and 10b located respectively at opposite sides of the intersection of bores 11 and 12 (Fig. 4).

Rotary meshing gears 15 and 16 (Fig. 4) are located snugly in the bores 11 and 12, respectively, for pumping fluid from the suction inlet passage 17, formed in housing member 10 at one side of the meshing gears, around to the high pressure discharge passage 18, formed in housing member 10 at the opposite side of the gears.

Casing end plate 14 is formed with a cylindrical recess 67 (Fig. 1) at which is located fixedly a flanged bushing 68 which supports for rotation an integral journal 19 projecting from one end of gear 15. Bushing 68 is formed with atransverse annular flange 20 locatedin housing bore 11 between thesadjacentend face of gear 15 and the. .inner,,face .21. of housing .end plate. 14. This flange is cylindrical around substantially its entire periphery to fit snugly in housing bore 11, with a diameter at its cylindrical portionequalto the .outendiameter of gear 15, and is flattened at its lower end, at the intersection of the :housing bores Hand 12.

.Gear .15 has an. internal .splinedmconnec'tion. to a rotary drive shaft. 22 which. extends through a'suitable fluid .seal, indicated generally .1at;523, to .aconnection to a prime mover, such .as zanelect'ric motor.

At the correspondingemhof-geari16,; an :integral journal 24 -prjectsinto .a'rbearing-rbushing 25 fixedly located in a recess 26 formed in the housing. end :plate .14. Bushing 25 supports gear jOLI111211124TfQ1. rotation. At :itsinner: end this bushing :is formedvwithan integral::transverse annular flange .27, which 'is positioned in. housing bore between the adjacent end face of gear 16 and the innerface 21: of housingend-plate .14. ZIThis:bushingflange is cylindrical around: itsentireperiphery: to fit snugly within bore:12,.except at its upper-end, =.at;the intersection of bores :llsand 12, where, it, is, flattened to ahut'snuglyagainst'the. flattened lower end ofjthe flange'20 on ,bushing18. At. its cylindrical portion, bushing flange .27 has a. diameter. equal to the outer diameter of gear 16.

At its opposite end, the upper gear:15.carrieszanintegral journal 28 which is .suppontedzfor.rotation.by a' fixed bushing 29,-whose.configuration-isibest seen in3Fig..2. .This bushing includes a cylindrical .sleeve portion "disposed snugly within a complementary recess.30 formedin the housing end plate 13. An enlargedrtransverse annular flange 31 on;bushing 29 is;receiv e'd.i11housing bore 11 and abuts against the inner-face 32 of:the end plate. 13. This flange is cylindrical around substantiallyitsentire periphery and is complementary to the .bore .11 50.38210 .besnug- 1y received therein. At itsilower end, .at;the.intersection of housing bores 11 and,12, the bushing. flange 31 is flattened. vImmediatelyadjacent; its :flattened lower. end, at the low pressure side of the pump the bushing flange 31 is.formed with anarcuaterecess .33, for.a purpose which will be apparent. hereinafter. .At ,thefront. of flange 31, the bushing 29;isformed-withanannular nose. 34 which at its forward end is spaced from .theadjacent end face ofgearlS.

In like manner, the lower gear.;16s.carries .anintegral iournal35 which is supported .fonrotatiombyafixed bushing 36. Bushing 36-has a cylindricahsleeve portion disposed snugly within a complementary recess 37 in housing end plate 13.extending .awaynfroml'itsjnner face 32. Bushing 36 is formedwithv anintegral enlarged transverse flange 38 located in housing bore .12;and abutting against the inner face 32 of end plate 13. Flange 38 is cylindrical aroundrsubstantially itsentireperiphery to: fit snugly in bore 12,;and;at.its upperqendzis flattened to abut snugly against theflattened-lower end;of.bushing flange 31, at the intersectiomof theihousingr-bores .11 and.12. Immediatelyadjacent its flattened .upperqend ,thebushing flange 38 is formed with;an,arcuate recess .39 inv its periphery, which forms a substantially :semi-circular opening with the corresponding recess 33 .in .the bushing flange 31. Bushingi36;is also formedwith anannular nose 40 projectingbeyond the .frontzof flange 38 and having the forward endthereofspacedEfrom the adjacent end face of gear 16.

The ;pressure .loadedmechanism in the present invention is..in-the.form:of :an irregularly shaped member 50 having-areducedcylindrical stem 51 at its rear, or outer end, which extends :through the arcuate peripheral recessesat ;33.and.39 in.the;.bushing flanges 31, 38 and is received in a complementarycylindrical. recess 52' formed inathe end plate .13textending ;away from the inner face 32 thereofzimmediatelybehind theserecesses in the bushing iflanges. .At .the .front .end ;of stem 151,..tl1e pressure member .is formed .with a .flat transverse shoulder 53 i(-I.Tjgs.::.-and-.6,), which isJQcated between-thefmntfaces of the bushing flanges 31 and 38 and the adjacent end faces of gears15 and 16. The shoulder 53 extends across the front of these bushingflanges and has arcuate top and bottom edges 54 and -55 respectively shaped complementary to the annular nose portions 34 and 40 on the bushings and which guidingly engage the same. Shoulder 53 extends across the mesh. point of the gears and terminates just beyond this mesh point at the high pressure side ,of'the gears. At its..opposite end the shoulder terminates in a forwardly extending arcuate end wall 56 shaped complementary to, and snugly received in, the arcuate recess 10a formed in casing member 10 atthe low pressure side of the intersection of housing bores 11 and 12. From Fig. 4 it will be apparent that shoulder 53 on the pressure .,member is disposedcontiguous to the adjacent end faces of gears 15 and 16 at the low pressure side of the gears and extends around the annular nose portions 34 and 40 to a point beyond the respective intersections of housing :recess 10a with the bores 11 and 12 but well short of the pump .centerline through the gear axes. The shoulder also extends between the annular nose portions beyond thepoint of engagement ,of the gears and well over toward the high pressure'side of the pump.

The pressure member forwardly of .the shoulder 53 projects snugly between the meshinggears entirely-across the gear peripheries, having arcuate faces 57, 58 shaped complementary to the outer diameters of the respective gears and extending contiguous to the gear peripheries, the forward end of the pressure member extending partially acrossthe peripheral facesofthe flanges 20 and 27 at the inlet side of the pump. vA fluid passage 59 extends through the pressure member to pass fluid from the suction inlet 17 to the gears at their low pressure side, immediately adjacent their intersection. It will be noted from Fig. 4 that shoulder 53 extends contiguous to the adjacent endfaces of the gears from the portions of the gears Which'at their peripheries communicate with the flow passage 59 and also extends along portions of the gears (immediately above and below passage 59 in Fig. 4) which at their peripheries are immediately adjacent flow passage 59-but out of communication therewith. These latter portions of the gears which are out of communication with passage 59 are under higher fluid pressure,so that there would be a tendency .for leakage from these high pressure areas across the end faces of the gears to the low pressure area at passage 59. 1Shoulder'53, however, is pressure loaded against the gear end faces to substantially-prevent such leakageas described hereinafter.

At its inner, or forward end, the pressure member terminates ina flat end face 60 positioned in spaced relation to the inner face .21 of housing end plate 14 so that the pressure member may move longitudinally in the housing to bring the shoulder 53 into abutting engagement with the adjacent faces of the gears 15 and 16. The arcuate upper and lower faces '57 and 58 on the pressure member 50 engage :snugly against the cylindrical peripheries of the bushing flanges 20 and 27, respectively.

Each of the flanges 20,27, 31 and 38 on the bushings 68, 25, 29 and 36 respectively-are thus snugly received in the bores 11 and 12 and serve as locatorsfor the casing member ltland the end plates 13 and 14 to aid in ac curately aligning the several parts of the casing during assembly. Additionally, the bushing'flanges 20 and 27 serve to locate and guide the inner end of pressure member 50 when thepump is assembled. The arcuatesurfaces 54 and 55 on the shoulder 53 slidably engage the annular nose portions 34 and 40 .to thereby guide the outer end of the pressure member 50. Thus,-the pressure member is guided at its inner and outer ends by the flanged bushings so that the pressure member does not contact the rotating journals on the drive and driven gears. Since the pressure member is separate from the bearings for the journals .on the gears, .the hydraulic forces acting on the. gears are :not :transmitted .to the 4. pressure. member.

These hydraulicpressures, if applied to the pressure loading device would be perpendicular to the path of movement thereof and would therefore press the pressure member against the casing and prevent movement thereof longitudinally of the casing and consequently prevent the pressure loading member from forming a proper seal on the ends of the gears.

A coil spring 62 is under compression in recess 52 in end plate 13 and biases the pressure member 50 toward the adjacent end faces of the gears. The pressure member 50 is formed with a passage 63 extending from the front face of shoulder 53 through to the outer end of stem 51, so that the outer face of this stem is in fluid communication with the suction inlet side of the pump, thereby establishing low fluid pressure acting against this portion of the pressure member.

A fluid pressure chamber .64 between the gears and the bushing flanges 31 and 38 communicates with the high pressure discharge passage 18 and applies the relatively high discharge pressure across the entire back face of the shoulder except for that portion thereof from which the stem extends. Thus, these end faces of the gears are exposed to high fluid pressure, except at the shoulder 53 on the pressure member 50, which has its outer face remote from the gears exposed to the pressure in chamber 64. The shoulder 53 is in pressure contact with the ends of the gears and prevents free communication between the fluid pressure chamber 64 and the end portions of the gears contacted by the shoulder. The pressure on those portions of the gear ends is therefore determined by the pressure in the interdental spaces on the gears, which pressure is equal to the inlet pressure adjacent the inlet passage 59 and progressively increases in the direction of rotation of the gears and becomes equal to the pressure in the chamber 64 at the end of the shoulder 55 remote from the inlet passage 59. The teeth on the gears afford free fluid communication between corresponding areas on opposite sides thereof so that the fluid pressure acting on the opposite sides of the gear are substantially equal and produce no resultant end thrust on the gears.

The pressure acting on the inner side of the shoulder 53 is thus zero adjacent the inlet passage 59 and increases therealong to a pressure equal to the pressure in the chamber 64 at the ends thereof remote from the inlet passage. Additionally, that part of the shoulder which projects between the annular nose portions 34 and 40 and beyond the point of mesh of the gears is subjected to discharge pressure. The outer face of the shoulder 53, except for that portion from which the stem 51 extends, has the relatively high pressure in the chamber 64 applied thereto, and the end of the stem 51 has suction or inlet pressure applied thereto. The area of the end of the stem 51 exposed to the low suction pressure is chosen with respect to the remainder of the area of the shoulder 53 so that the total hydraulic force acting on the back side of the shoulder and the end of the stem is the same or only slightly greater than the hydraulic force acting on the front of the shoulder. With this arrangement, the shoulder 53 is pressure loaded against the adjacent end faces of the gears by the spring 62 which also pressure loads the gears against the bushing flanges 20 and 27 at their opposite end faces, the differential between the hydraulic force acting on the back of the shoulder and the hydraulic force acting on the front thereof aiding the pressure loading of the spring.

Operation In the operation of the above-described pump, fluid drawn into the pump through the inlet passage 17 passes posite side of the gears and from there passes to the discharge outlet 18.

Initially spring 62 biases the pressure member 50 to position the front face of its fiat shoulder 53 contiguous to the adjacent end faces of the gears to establish a pumping seal thereat. When the pump is placed in operation, the back side of shoulder 53 is exposed to the high fluid pressure in chamber 64 and the end of the stem 51 has suction pressure applied thereto. The pressure loading force on the pressure member 50 is, of course, determined by the area of this pressure member exposed to high pressure fluid at the back side of the shoulder and the area of the end of the stem 51 exposed to the suction pressure. The area of the end of the stem is chosen by suitable design of the pressure member to produce a resultant hydraulic force acting on the back of the shoulder which is only slightly greater than the resultant hydraulic force acting on the front of the shoulder. Therefore, the spring 62, aided by the slight excess hydraulic force acting on the back of the shoulder, maintains the shoulder pressure loaded against the adjacent gear end faces. Obviously, as the pressure acting on the back of the shoulder varies with changes in the pump output pressure, the pressure acting on the front of the shoulder changes in a similar manner so as to maintain substantially the same small relative pressure unbalance between the inner and outer faces of the shoulder. This pressure unbalance aided by the compression spring 67 maintains the desired pumping seal at the end faces of the gears at all times and thereby provides an effective pumping seal in which the end faces of the gears have merely a running clearance, while at the same time there is not excessive frictional drag between the gears and the pressure member.

Since the spaces between the gear teeth provide free fluid communication thereacross, the fluid pressure at corresponding areas on opposite sides of the gears will be equal and counterbalance each other. Therefore, the only force acting on the gears to urge the latter against the bushing flanges 20 and 27 is the force of the spring 62 acting on the pressure member and the aforementioned hydraulic unbalance acting on the shoulder 53. The force applied on the pressure member 50 to urge the latter against the gears is thus transmitted to the gears and urges the latter against bushing flanges to form a running seal thereat.

Because of the snug fit of the pressure member 50 between the housing at recess 10a and the peripheries of the gears, the pressure member establishes a close running clearance for the peripheries of the gears which minimizes leakage of fluid therearound from the high pressure side of the gears back to the low pressure side thereof.

From the foregoing, it will be apparent that the novel pressure loading arrangement is effective to prevent leakage, across the end faces of the gears and around the gear peripheries, from the high pressure side of the pump to the low pressure side of the pump. The pressure member 50 has only as much face area at shoulder 53 confronting the end faces of the gears as is necessary to provide an effective pumping seal thereat, so that the frictional drag between the gears and the pressure member is reduced to a minimum, thereby reducing correspondingly the torque required to drive the pump. Since the pressures acting on opposite sides of the shoulder 53 are substantially balanced, the resultant force acting on the pressure member is small. Moreover, the stem 51 on the pressure member is located so that the small pressure unbalance that is provided is substantially symmetrical thereto, so that there is substantially no tendency for the pressure member to tilt away from the adjacent end faces of the gears, as in conventional pressure loaded bushings.

In addition, the gear drag forces on the shoulder 53 of pressure member 50 cancel each other out because of the opposite rotation of the gears.

With the novel pressure loading arrangement of Figs. 1-6, as the bearings for the gears wear, the resultant force actingon thegears. due to discharge pressure-will bein a direction to urge :the gears toward the arcuate faces ,57 and58.0n the pressure member 50 so that the latter .will be worn by the gearteeth to conform closely to the gear peripheries as the gears shift position within thepump housing. This action willtend to prevent the chewing out of the housing bores 11 and 12 themselves, so that after the wear has become excessive the pump may be made as good as new by replacing the gears, bearing bushings and pressure member, without the necessity of replacing the pump housing itself.

'It is to be understood that the pump of Figs. 1-6 may also be operated with the pressure member 50 located adjacent the high pressure discharge passage. Thus, if the housing passage 18 were made the suction inlet and the housing passage 17 were made -,the discharge outlet and the area of the stem chosen so as to obtain substantial hydraulic balance on the shoulder 53, the pressure member 59 would be urged into engagement withjthe adjacent gear end faces by the spring 62 and be eifective for its intended purpose. of providing a pumping seal across the adjacent end faces of the gears and pressure loading the opposite end faces of the gears against-the adjacent bearing bushing flanges to establish a pumping seal thereat. In view of this, therefore, it should be obvious that this pressure loading arrangement may also be used where the device is operated as a fluid motor, as well as for the pump operation described above.

In the alternative embodiment of the present invention, shown in .Figs. 7 and 8 the arrangement of the gears and the pressure bushings may be identical to that shown in Figs. 1-6. Therefore, reference may be had to Figs. l-6 for these'details. The pressure member, however, is in the form of a pair of fiat, intersecting arcuate segments 70 and 71, which are snugly received between the walls of the cylindrical, intersectingjhousing bores 111 and 112 and the cylindrical reduced nose portions 134 and 140 on the corresponding pressure bushings. The flat segments 70 and 71 on thepressure member have their inner faces positioned contiguous to, the adjacent end faces of the gears 115 and 116, respectively. As best seen in-Fig. 7, thesevflat segments 70 and 71 extend contiguous to the adjacent end faces of the gears from portions of the gears whichat'ttheir peripheries communicate with'the suctioninlet.passage.117 across the mesh point of the gears, terminating thereat immediately beyond the meshpoint of the gears, and from the portions of the gearswhich .at :their peripheries communicate with the .inletpassage 117 to portions of the gearswhich at their peripheries are immediately adjacent the inlet 117 (directlyabove and below it ,in ,F ig. 7), ,but out of communicationtherewith, terminatingv thereat :well short of the center-lineof the pump.

An integral-cylindrical stem- 151 projects from;the back face oftheflat segments 70 and 71 and is snugly;received in a complementary recess 152 formed in the housing end wall 113. A- passage 163 through the pressure member effects communication between the outer end of stem 151 and the suction inlet 117. An O-ringseal72is. provided to prevent vleakagealong .the periphery ofthe stem 151 on:the pressure. member. .Acoil spring162 isunder compression in the housing recess l52-and. biases the pressuremember to position the inner faces,of,its .flat segments 7t) and 71 against .thez adjacent end .faces,of the gears.

In this assembly,ithegpressure member. does notextend across .the peripheries :of: the gears, but :merely .across portions ,of tbe gearendfaces -,at'. one :end thereof. .Be-

.cause. of:;this, :;the.'zcylindrical -housingbores 111 and 112 intersect each other as in conventional pumps, andgthere are no housing. chambers corresponding .to a ,and 10h inthe. firstzembodiment.

Thus, the housing itself is more similar to standard gear pumphousingsthanisthehous- .ing in Figs. 1+6.

harg pressu e i appliedte h ba k fa ep th fl mes-- men and 1.1 am sucti P s ur is ppl d t the end,of ,thestem. As .inthe preceding embodiment, the area ofthestern is proportioned relative to the area of the segments Y70 and 71 so that the total hydraulic force actingon the stem and the back of the segments is equal to or only slightly greater than the total hydraulic force acting on the inner side, ofthe segment. Thus, the segments 7.0..and 71 are urged against the adjacent end facesof thegearsonlvby the force of the spring 162 as aided by the small hydraulic pressure unbalance acting thereon. The hydraulicpressures on corresponding areas at oppositeendiaces of the gears are substantially equal. Therefore the onlyforce acting on the gears to urge them into engagement with the bushing flanges is the pressure applied to the gears by the pressure member. The pressure member is therefore pressed into contact with the gears and thelatter are pressed into contact with the bushing flangesby an equal force, which force is substantially independent of variations in discharge pressure.

It is to beunderstood. that the pressure loading arrangement of Figs. 7 and 8 is just as readily adaptable to providing the pumping seal at the low pressure side of the gears asat the high pressure side, as is the arrangement of Figs. 1 6, ,andis equally adapted to pump or fluid motor operation.

It will be apparent that the pressure member of Figs. Tand 8 is quite simple in construction. Because of this, it maybe .die cast or formed by. powderedmetallurgy techniques at ,verynominal cost. Furthermore, because of the mannenjdwhich thispressuremember fits snugly in the housing bores, the housing itself is essentially the standardhousing for nonrpressure-loaded pumps, and the rest of the pump other than the pressure member would cost no more than a conventional non-pressure-loaded pump. V

While in; the, foregoing description and the accompanying drawings thererhave been disclosed two specific preferredembodirnents of this invention, it isto be understood that various modifications, omissions and refinements which depart from the disclosed embodiments may be adopted without departing-from the spirit and scope of the present invention.

'I'claim:

l. Agear pump comprising a housing having parallel intersecting pump bores therein, a pair of meshing gears disposed in said pump bores and having gear shafts rotatably supported in said housing, said housing having a high pressure and, a low pressure passage at opposite sides of the mesh points ofthe gears, said housing including means defining one-endwall extending contiguous to one of the and faces ofeach of said gears and another end Wall spaced from the other of the end faces of each of said gears and defining a fluid pressure chamber there- .with, a; generallyN-shaped pressure member including a pairof arcuate intersecting segments slidably, disposed in said; pressure chamber between said pump bores andsaid gear-shafts {or -movement towards said. other end faces of the gears,, said arcuate segments having flat faceson one sidethereof extending contiguous to ohlyt aportion of said other end faces of the gears, from themeshspoint thereof andacross said other endfaces of the portions of the gears communicating. with one of said pressure passages to a point adjacent said one pressure passage and angularly spaced less than from the mesh point of the gears, to seal said portions of said other gear end faces from the fluid pressure in said chamber, said chamber communicating with the other of said pressure passages and with the portions of said other end faces of the gears which are not contiguous to said pressure member, means definingan area at the other side of said pressure -rnember adjacent the intersection of said arcuate segments and sealed from the-remaining area at said other side of said pressure membenand a passage extending through said pressure member from said one side thereof for supplying fluid under pressure from said one pressure passage to said area on said other side of the pressure memher.

2. A gear pump comprising a housing having parallel intersecting pump bores therein, a pair of meshing gears disposed in said pump bores and having gear shafts rotatably supported in said housing, said housing having a high pressure and a low pressure passage at opposite sides of the mesh points of the gears, said housing including means defining one end wall extending contiguous to one of the end faces of each of said gears and another end wall spaced from the other of the end faces of each of said gears and defining a fluid pressure chamber therewith, a generally V-shaped pressure member including a pair of arcuate intersecting segments slidably disposed in said pressure chamber between said pump bores and said gear shafts for movement towards said other end faces of the gears, said arcuate segments having flat faces on one side thereof extending contiguous to only a portion of said other end faces of the gears, from the mesh point thereof and across said other end faces of the portions of the gears communicating with one of said pressure passages to a point adjacent said one pressure passage and angularly spaced less than 180 from the mesh point of the gears, to seal said portions of said other gear end faces from the fluid pressure in said chamber, said chamber communicating with the other of said pressure passages and with the portions of said other end faces of the gears which are not contiguous to said pressure member, a piston rigidly secured to the other side of said pressure member adjacent the intersection of said arcuate segments, said housing having a recess therein slidably receiving said piston and sealing the area at the end of said piston from the remaining area at said other side of the pressure member, and a bore extending through said pressure member and piston and communicating with said recess for supplying fluid from said one pressure passage to the area on the end of said piston.

3. The combination of claim 2 wherein the area of said piston is proportioned to the remaining area on said other side of said pressure member so that the total hydraulic force acting on said other side of the pressure member substantially equals the total hydraulic force acting on said one side of said pressure member.

4. A gear pump comprising a housing having parallel intersecting pump bores therein, a pair of meshing gears disposed in said pump bores and having gear shafts rotatably supported in said housing, said housing having a high pressure and a low pressure passage at opposite sides of the mesh points of the gears, said housing including means defining one end wall extending contiguous to one of the end faces of each of said gears and another end wall spaced from the other of the end faces of each of said gears and defining a fluid pressure cham ber therewith, a generally V-shaped pressure member including a pair of arcuate intersecting segments slidably disposed in said pressure chamber between said pump bores and said gear shafts for movement towards said other end faces of the gears, said arcuate segments having flat faces on one side thereof extending contiguous to only a portion of said other end faces of the gears, from the mesh point thereof and across said other end faces of the portions of the gears communicating with one of said pressure passages to a point adjacent said one pressure passage and angularly spaced less than 180 from the mesh point of the gears, to seal said portions of said other gear end faces from the fluid pressure in said chamber, said chamber communicating with the other of said pressure passages and with the portions of said other end faces of the gears which are not contiguous to said pressure member, means defining an area at the other side of said pressure member adjacent the intersection of said arcuate segments and sealed from the remaining area at said other side of said pressure member, a passage extending through said pressure member from said one side thereof for supplying fluid under pressure from said one pressure passage to said area on said other side of the pressure member, said pressure member including an integral projection extending axially of the pump bores from said one side of said pressure member and having arcuate faces extending completely across the gear peripheries in close running fit therewith, said axial projection having a passage extending therethrough and communicating said one pressure passage with the gears adjacent the mesh point thereof.

5. A gear pump comprising a housing having parallel intersecting pump bores therein, a pair of meshing gears disposed in said pump bores and having gear shafts rotatably supported in said housing, said housing having a high pressure and a low pressure passage at opposite sides of the mesh points of the gears, said housing including means'defining one end wall extending contiguous to one of the end faces of each of said gears and another end wall spaced from the other of the end faces of each of said gears and defining a fluid pressure chamber therewith, a generally V-shaped pressure member including a pair of arcuate intersecting segments slidably disposed in said pressure chamber between said pump bores and said gear shafts for movement towards said other end faces of the gears, said arcuate segments having flat faces on one side thereof extending contiguous to only a portion of said other end faces of the gears, from the mesh point thereof and across the end faces of the portions of the gears communicating with one of said pressure passages to a point adjacent said one pressure passage and angularly spaced less than from the mesh point of the gears, to seal said portions of said other gear end faces from the fluid pressure in said chamber, said chamber communicating with the other of said pressure passages and with the portions of said other end faces of the gears which are not contiguous to said pressure member, means defining an area at the other side of said pressure member adjacent the intersection of said arcuate segments and sealed from the remaining area at said other side of said pressure member, a passage extending through said pressure member from said one side thereof for supplying fluid under pressure from said one pressure passage to said area on said other side of the pressure member, a pair of bushings in said first end wall supporting said gear shafts and having integral transverse flanges shaped complementary to said pump bores, said pressure member including an integral projection extending axially of the pump bores from said one side of said pressure member and having arcuate faces extending completely across the gear peripheries in close running fit therewith and at least partially across the peripheries of said flanges to be guided thereon, said projection having a passage extending therethrough communicating said one pressure passage with the gears adjacent the mesh point thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,044,873 Beust June 23, 1936 2,105,259 Oshei Jan. 11, 1938 2,146,395 Horton Feb. 7, 1939 2,211,154 Oshei Aug. 13, 1940 2,622,534 Johnson Dec. 23, 1952 2,641,192 Lindberg June 9, 1953 2,682,836 Orr July 6, 1954 2,695,566 Compton Nov. 30, 1954 2,728,301 Lindberg Dec. 27, 1955 2,742,862 Banker Apr. 24, 1956 FOREIGN PATENTS 659,600 Great Britain Oct. 24, 1951 1,047,792 France July 29, 1953 

